Showing papers in "Environmental Entomology in 1986"
TL;DR: A BASIC computer program (DEGDAY) for calculating degree-days on microcomputers is presented and various errors arising from these factors are discussed in relationship to error attributable to differences between actual and estimated degree- days.
Abstract: A BASIC computer program (DEGDAY) for calculating degree-days on microcomputers is presented. The program calculates heating degree-days with the rectangle, triangle, and sine wave methods and calculates cooling degree days with the sine wave method. Assumptions and approximations associated with degree-day calculations are noted. In particular, eight factors affecting degree-days are discussed: 1) substrate availability, 2) enzyme availability, 3) approximations in laboratory estimates of development, 4) approximations in calculating the developmental minimum, 5) approximations in calculating a developmental maximum, 6) approximations in using single values for thresholds, 7) thermoregulation, and 8) limitations of temperature data. The various errors arising from these factors are discussed in relationship to error attributable to differences between actual and estimated degree-days.
316 citations
TL;DR: Effects of agroecosystem diversification on searching behavior and success of arthropod natural enemies are poorly understood and pest control by specialist enemies may be more effective in less diverse agroECosystems if concentration of host plants increases attraction or retention of these enemies.
Abstract: Effects of agroecosystem diversification on searching behavior and success of arthropod natural enemies are poorly understood. Crop diversification may increase generalist enemy effectiveness by increasing alternate food or prey availability, as predicted by the enemies hypothesis. But diversification may also reduce enemy searching efficiency and destabilize predator/prey interactions. Additionally, specialist enemies, often important in biological control programs, may be particularly sensitive to vegetation texture. Pest control by specialist enemies may be more effective in less diverse agroecosystems if concentration of host plants increases attraction or retention of these enemies.
208 citations
TL;DR: A simulation model was developed to predict how long it would take a pest to adapt to two antibiotic, host-plant resistance factors if they were deployed sequentially, as a cultivar mixture, or combined in a single pyramided resistant cultivar, indicating that no single deployment strategy was most durable in all pest/cropping system combinations.
Abstract: A simulation model was developed to predict how long it would take a pest to adapt to two antibiotic, host-plant resistance factors if they were deployed sequentially, as a cultivar mixture, or combined in a single pyramided resistant cultivar. Results indicated that no single deployment strategy was most durable in all pest/cropping system combinations. When relative fitness of the insect pest on plants with both resistance factors was linearly related to the number of adaptive alleles that the insect possessed, sequential release of two cultivars with different single resistance factors or mixed planting of these two cultivars was expected to provide weaker but more durable resistance than pure plantings of a cultivar into which both resistance factors had been pyramided. If totally susceptible plants are grown adjacent to the pyramided cultivar in a ratio that causes the mean fitness of insects with no adaptive alleles to be equivalent to their mean fitness in the sequential-release plan, the durability of all three strategies is similar. If alleles for adaptation are recessive and epistasis is strong enough to make the two resistance factors largely redundant in plants possessing both factors, pyramided deployment of resistance factors is often expected to be much more durable than a sequential or mixed release. Durability of the pyramided cultivar is enhanced by adding some totally susceptible plants to the system. Structural linkage of the two insect loci would reduce durability of such a pyramided cultivar, but it would usually be more durable than sequential or mixed releases.
149 citations
TL;DR: A computer simulation model was developed to mimic ecological/genetic interactions between Hessian fly populations and resistant winter wheat, finding that interpolating a pyramided resistant cultivar with some totally susceptible plants offers the highest relative durability in most cases.
Abstract: In an attempt to determine what strategies of resistant germ plasm deployment would most successfully inhibit Hessian fly, Mayetiola destructor (Say), adaptation to wheat resistance factors while offering significant crop protection, a computer simulation model was developed to mimic ecological/genetic interactions between Hessian fly populations and resistant winter wheat. Durability of the following resistant germ plasm deployment strategies was examined: 1) sequential release of two pure cultivars, each with a single resistance factor, 2) release of a random spatial mixture of these two cultivars, 3) release of a pure cultivar in which both resistance factors were present in each plant (pyramided), and 4) modification of each of the above deployment strategies by addition of totally susceptible wheat to the system. Effects of temporal and spatial characteristics of the mixtures were also explored. Interpolating a pyramided resistant cultivar with some totally susceptible plants offers the highest relative durability in most cases, and is predicted to last >400 fly generations under some conditions.
127 citations
TL;DR: Female flower thrips showed a faster rate of egg discovery than did larvae, but larval thrips had a higher upper limit for predation than did adult females, which was exhibited by a shorter egg handling time for larvae.
Abstract: Larvae and adult females of the western flower thrips, Frankliniella occidentalis (Pergande), showed a functional predatory response to increases in density of spider mite eggs. Female flower thrips showed a faster rate of egg discovery than did larvae, but larval thrips had a higher upper limit for predation than did adult females, which was exhibited by a shorter egg handling time for larvae. Spider mite webbing on the eggs and leaf surface significantly inhibited predation by thrips larvae. Flower thrips are omnivorous opportunists, because they can resort to herbivory when mite eggs are absent or scarce. Thrips are important as herbivores, predators, and prey for other predators. Information on predation by flower thrips will lead to a better understanding of their impact on spider mite populations in the field.
125 citations
TL;DR: Differences between the high- and low-leptine clone from each accession were significant for all five resistance parameters, and these differences appeared to be directly related to the concentration of foliar leptines.
Abstract: The role of leptine glycoalkaloids in resistance to Leptinotarsa decemlineata (Say) was studied with Solanum chacoense Bitt. clones that had been selected for extremes of leptine level. Three high-leptine (120–306 mg/100 g fresh weight) clones, one from each of three accessions, were compared with three low-leptine (0–51 mg/100 g) sib-clones for number of adults and feeding damage in the field, adult feeding rate on leaf disks, and larval development on detached foliage. Number of adults per plant on the six clones ranged from 1.5 for the clone with the highest leptine level (306 mg/100 g) to 37.5 for a clone lacking even a trace of these rare glycoalkaloids. There were also wide and significant differences among the six clones for adult feeding damage, adult feeding on leaf disks, larval development rate on detached foliage, and survival to adult eclosion. Differences between the high- and low-leptine clone from each accession were significant for all five resistance parameters, and these differences appeared to be directly related to the concentration of foliar leptines.
116 citations
TL;DR: Western flower thrips, Frankliniella occidentalis (Pergande), a known vector of tomato spotted wilt virus, was found to be associated with 48 plant species growing within the Kula vegetable-growing region on the island of Maui, Hawaii.
Abstract: Western flower thrips, Frankliniella occidentalis (Pergande), a known vector of tomato spotted wilt virus, was found to be associated with 48 plant species growing within the Kula vegetable-growing region on the island of Maui, Hawaii. High populations of F. occidentalis were found within the blossoms of three woody legume species, Leucaena glauca (L.) Benth., Prosopis pallida (Humb. & Bonpl ex Willd.), and Acacia decurrens Willd., and on crisphead lettuce, romaine, tomato, and cabbage. F. occidentalis also occurred on 12 common weed species of lettuce fields. Thrips populations associated with L. glauca were greatest at low elevations (200–450 m) in June and at higher elevations (500–640 m) in July.
115 citations
TL;DR: In this paper, the green peach aphid (GPA) was compared on potatoes with different levels of nitrogen (N) (56, 84, 140, and 224 kg N/ha).
Abstract: Population parameters of the green peach aphid (GPA), Myzus persicae (Sulzer), were compared on potatoes fertilized with different levels of nitrogen (N) (56, 84, 140, and 224 kg N/ha). Abundance of GPA was not significantly different among N treatments. The population growth rate of GPA increased with the level of N applied. However, the highest level of N (224 kg N/ha) reduced the rate of population growth. Populations grew more rapidly on potatoes fertilized with a split-applied intermediate N treatment (56 + 84 kg N/ha) than on potatoes fertilized with 56, 56 + 28, or 56 + 168 kg N/ha. Additionally, populations of GPA grew more rapidly when 224 kg N/ha was applied in one application than when applied in two applications. The rate of population growth was positively correlated with the concentration of free amino acids in leaves. The within-plant distribution of GPA was similar for all treatments. GPA were consistently more abundant on the lower leaves in each treatment. Population growth rates were greater on lower leaves than on other leaves in most N treatments. Population growth rates were negatively correlated with foliar concentrations of free amino acids within leaves of different vertical zones, but were positively correlated with foliar concentrations of nitrate N within leaves of different vertical zones. Also, population growth rates were positively correlated with the percentage of the total organic N pool composed of amino N within leaves of different vertical zones. Implications of variable host-plant nutritional quality in pest management are illustrated.
106 citations
TL;DR: Research on flight activity of the western corn rootworm, Diabrotica vir gifera virgifera LeConte, is presented and periodicity was observed for both types of flight.
Abstract: Research on flight activity of the western corn rootworm, Diabrotica virgifera virgifera LeConte, is presented. Field-captured, mated females, aged 2–15 days posteclosion, were flown on flight mills linked to a microcomputer data-recording system. Flight duration ranged from 1 to 17 min for trivial flights; sustained flights lasted up to 4 h. Sustained flights were not made after females were 9 days old. Maximum distances of 24 km for one flight and 39.6 km for all flights during a 24-h period were recorded. Average speed of flight was 16 m/min for trivial fliers and 49 m/min for sustained fliers. Periodicity was observed for both types of flight; greatest flight activity occurred from 1800 to 2400 hours.
100 citations
TL;DR: Five entomopathogenic Hyphomycetes were tested under field conditions for biological control of brown planthopper, Nilaparvata lugens (Stal), in rice and the mycelium preparation sporulated on the plant and was as effective as the conidia suspension in infecting brown planTHopper.
Abstract: Five entomopathogenic Hyphomycetes were tested under field conditions for biological control of brown planthopper, Nilaparvata lugens (Stal), in rice. Suspensions of conidia of Metarhizium anisopliae (Metsch.) Sorokin, M. flavoviride Gams & Roszypal, Beauveria bassiana (Bals.) Vuill., and Hirsutella citriformis Speare were applied at a rate of 4–5.1012 conidia per ha. In addition, M. anisopliae and Paecilomyces lilacinus (Thorn) Samson were applied as preparations of dry mycelium at a rate of 1.5–2 kg/ha. Mortality due to fungus infection ranged from 63 to 98% 3 weeks after application. There were no consistent differences between fungus species. The mycelium preparation sporulated on the plant and was as effective as the conidia suspension in infecting brown planthopper. Hyphomycetous fungi should be evaluated further for control of brown planthopper in rice.
83 citations
TL;DR: It was confirmed that first instars do not feed, so aggregation had no role in nutrient intake, and aggregation apparently does not function as a means of contacting essential symbiotes.
Abstract: The role of aggregation in mediating the ecological parameters that influence survival and development in first-instar southern green stink bug, Nezara viridula (L.), was examined. Aggregated nymphs were able to survive and develop more rapidly than isolated nymphs at low relative humidities. Aggregation appeared to facilitate intake of atmospheric water and protect against desiccation. An acceleration of development in aggregated nymphs was observed at low temperatures. It was confirmed that first instars do not feed, so aggregation had no role in nutrient intake. Aggregation apparently does not function as a means of contacting essential symbiotes. Adherence to a substrate was facilitated by aggregations of up to 10 nymphs, at which point aggregation became multilayered. Aggregated nymphs suffered less predation by Podisus maculiventris (Say) and Solenopsis invicta Buren. Individuals as well as groups of nymphs were unpalatable to Hippodamia convergens Guerin-Meneville. Monomorium minimum (Buckley) apparently learned nonpreference of first instars while Tertamorium guineense (F.) and Pheidole dentatum Mayr were undeterred from foraging for nymphs over time.
TL;DR: High correlations were found among carabid activity, absolute density estimates of carabids, and number of lepidopteran larvae consumed in these corn agroecosystems, indicating that the technique demonstrated the potential of endemic predatory arthropods to reduce soil larvae pests significantly.
Abstract: Predation of lepidopterous larvae in corn agroecosystems was examined by observing tethered live larvae over several 24-h periods. There were significantly more attacks on larvae and more larvae were consumed in no-tillage systems compared with conventional tillage treatments. Predator activity (number of attacks) and predation were greatest at night and least in early afternoon over the entire season and generally increased as the season progressed. The soil insecticide phorate significantly decreased predators and number of pest larvae consumed for ca. 2 months after its application. Large carabids (≥ 15 mm) were the most important predatory arthropods in these agronomic systems; however, noncarabid species also provided significant predation. Significant correlations were found among carabid activity, absolute density estimates of carabids, and number of lepidopteran larvae consumed in these corn agroecosystems. These high correlations indicate that the technique demonstrated the potential of endemic predatory arthropods to reduce soil larvae pests significantly.
TL;DR: Plant feeding enhanced survival and shortened developmental times and preoviposition period of the predaceous pentatomid Podisus maculiventris (Say) and adults of both sexes were significantly larger and males were significantly heavier when potato foliage composed part of the nymphal diet.
Abstract: Plant feeding enhanced survival and shortened developmental times and preoviposition period of the predaceous pentatomid Podisus maculiventris (Say). When potato foliage was provided in addition to prey (Colorado potato beetle, Leptinotarsa decemlineata (Say), larvae) and water, preimaginal survival increased by 27.5%. Also, developmental time from second instar to adult eclosion was reduced by 2.4 days, and the preoviposition period was shortened by 1.4 days. Adults of both sexes were significantly larger and males were significantly heavier when potato foliage composed part of the nymphal diet. Plant feeding has both positive and negative biological features that should be considered in evaluating predaceous hemipterans as biological control agents.
TL;DR: Results indicate that newly hatched larve may use CO/sub 2/ to locate corn roots and there was no indication that a kinesis of any type was involved because velocities and turning rates were not significantly different among treatments.
Abstract: Responses of first-instar western corn rootworm to CO/sub 2/ and N/sub 2/ gas gradients were studied in a laboratory test arena. Number of larvae reaching the gas source, number of turns toward and away from the gas source, larval velocity, and number of turns per cm traveled were recorded. Larvae exhibited a positive chemotactic response to CO/sub 2/ but not N/sub 2/ or air. There was no indication that a kinesis of any type was involved because velocities and turning rates were not significantly different among treatments. Results indicate that newly hatched larve may use CO/sub 2/ to locate corn roots.
TL;DR: Results indicate that B. bassiana conidia retain high stability on beetle-attracting tubers if protected from sunlight, and use of fungal-treated tubers as a bait for control of chrysomelid beetles in cowpea-growing regions of Brazil or other countries is of potential importance.
Abstract: Conidia of two entomogenous fungi, Beauveria bassiana (Balsamo) and Metarhizium anisopliae (Metschnikoff) Sorokin, were applied to chrysomelid beetle-attracting tubers, Ceratosanthes hilariana Cogniaux, cowpea foliage, and cover slips and held outdoors under three exposure conditions of sunlight, or in the laboratory at 27 and 4°C, to determine the stability of conidia for potential use as microbial control agents of chrysomelid pests of grain legumes in Brazil. Under each exposure condition of sunlight (i.e., full, partial, or no protection from sunlight) conidia of B. bassiana survived best on the cucurbitaceous tubers, but the persistence of M. anisopliae conidia was more variable. In all cases for both fungi, exposure of conidia to full sunlight on all substrates was most detrimental to conidial stability; the half-life was generally 1–2 days and conidia were inviable within 1 week of exposure to sunlight. In contrast, conidia protected from sunlight survived much longer, in some cases remaining highly viable for ≥3 weeks. Results indicate that B. bassiana conidia retain high stability on beetle-attracting tubers if protected from sunlight. Use of fungal-treated tubers as a bait for control of chrysomelid beetles in cowpea-growing regions of Brazil or other countries is of potential importance.
TL;DR: A multinucleocapsid nuclear polyhedrosis virus (MNPV) was isolated during an epizootic in California's Merced County from a single larva of the beet armyworm, Spodoptera exigua (Hubner), and Restriction enzyme profiles of viral DNA indicate that this virus is markedly different from the Autographa californica (Speyer) MNPV and from Se MNPVs isolated from Egypt and the Netherlands, but is
Abstract: A multinucleocapsid nuclear polyhedrosis virus (MNPV) was isolated during an epizootic in California's Merced County from a single larva of the beet armyworm, Spodoptera exigua (Hubner). Occlusion bodies produced by this virus isolate, designated Se MNPV-608, measured 1.52 ± 0.11 µm ($\bar x$ ± SD) in diameter and most contained virion; with two to four nucleocapsids per envelope. Restriction enzyme profiles of viral DNA indicate that this virus is markedly different from the Autographa californica (Speyer) MNPV ( Ac MNPV) and from Se MNPVs isolated from Egypt and the Netherlands, but is; similar to other previously described Se MNPV isolates from California. Synchronous per o5 bioassays of the virus against neonate beet armyworm larvae demonstrated that Se MNPV 608 was highly virulent, with an ST50 of 57.39 ± 1.59 h ($\bar x$ ± SD), and more virulent for larvae of S. exigua than Ac MNPV (ST50 = 70.06 ± 2.66 h). Additionally, limited host range studies indicated that this isolate is specific for S. exigua no activity was apparent against larvae of the noctuids Heliothis virescens (F.), Trichoplusia ni (Hubner), or Spodoptera frugiperda (J. E. Smith).
TL;DR: The commercial preparation of Verticillium lecanii (Zimmerman) Viegas, ‘Vertalec’, was used to examine effects of a range of high humidities on transmission and sporulation using Myzus persicae (Sulzer) as host.
Abstract: The commercial preparation of Verticillium lecanii (Zimmerman) Viegas, ‘Vertalec’, was used to examine effects of a range of high humidities on transmission and sporulation using Myzus persicae (Sulzer) as host. All experiments were run at 20°C. Maximum transmission occurred only when relative humidity was 100% and free water was present. Lower humidities delayed and inhibited transmission, with little transmission occurring at 93% and none at 80% RH. Similarly, sporulation from disease-killed cadavers was delayed and inhibited below 100% RH, with virtually no sporulation at 80% RH. Spray deposits of ‘Vertalec’ required at least 36 h at 100% RH to become infectious. By 96 h after spraying, 94.5% of M. persicae had become infected. Implication of these results for control of aphids in greenhouses is discussed.
TL;DR: Experiments with artificial seeds containing various inhibitors of mammalian digestive proteinases demonstrated the applicability of the technique to evaluation of chemicals for effects on bruchid growth and development.
Abstract: An artificial seed system has been developed to evaluate putative allelochemicals and plant fractions for effects on growth and development of the bruchid, Callosobruchus maculatus (F.). The artificial seeds, which are prepared using flour from a bruchid-susceptible cowpea cultivar, permit rates of larva growth and development and survivorship comparable with those obtained with the intact parent cowpea seed. Experiments with artificial seeds containing various inhibitors of mammalian digestive proteinases demonstrated the applicability of the technique to evaluation of chemicals for effects on bruchid growth and development. Certain inhibitors (e.g., Bowman—Birk inhibitor from soybeans) have adverse effects on bruchid growth and development; others (e.g., lima bean trypsin inhibitor) have little or no effect.
TL;DR: The data suggest that both larval age and relative leaf age affect FAW response to endophyte-infected tall fescue.
Abstract: Differences in fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), larval preference for and development on fungal endophyte-infected (high incidence of infection) and uninfected (low incidence of infection) tall fescue, Festuca arundinacea Schreb., at three relative leaf ages were examined. Neonate larvae significantly preferred older, uninfected leaves to equivalent age infected leaves and fed more upon them in paired choice tests. Fourth-instar preference and consumption were not affected by infection status of leaves of equivalent age in 6- or 16-h choice tests. Eight-day larval weights were significantly higher for larvae reared on infected older leaves. Percent wet weight of fescue leaves was significantly higher in infected older leaves. Water-soluble carbohydrate and crude protein content did not differ between infected and uninfected leaves at any leaf age, although crude protein was significantly higher in young leaves. Loline alkaloid content was significantly higher in infected leaves and decreased as leaf age increased. The data suggest that both larval age and relative leaf age affect FAW response to endophyte-infected tall fescue.
TL;DR: This study demonstrates that Hylastes nigrinus, Pissodes fasciatus LeConte, and Steremnius carinatus are vectors of Verticicladiella wageneri Kendrick, the causal agent of black-stain root disease of Douglas-fir, Pseudotsuga menziesii (Mirbel) Franco.
Abstract: This study demonstrates that Hylastes nigrinus (Mannerheim), Pissodes fasciatus LeConte, and Steremnius carinatus (Boheman) are vectors of Verticicladiella wageneri Kendrick, the causal agent of black-stain root disease of Douglas-fir, Pseudotsuga menziesii (Mirbel) Franco. These insects, known associates of diseased hosts, wound and create suitable infection courts in susceptible hosts, carry inoculum in the field, and transmit the pathogen to hosts under laboratory conditions. Root systems of 12-year-old Douglas-fir, cut during precommercial thinning, were infested by these insects and were susceptible to V. wageneri infection for at least 7 months, confirming that V. wageneri may be introduced to thinned stands via these hosts. Male and female H. nigrinus created wounds suitable as infection courts on roots and root collars of crop trees for 1–2 years after precommercial thinning and may, therefore, introduce V. wageneri to thinned stands via these hosts. Insect-mediated transmission of V. wageneri to Douglas-fir by H. nigrinus in the field is documented.
TL;DR: It is suggested that weevil aggregations are formed in response to host volatiles and that weevils feeding increases amounts of these volatile released.
Abstract: Field tests were conducted with Hylobius abietis (L.) in Sweden during 1982 and 1983 to study how weevils feeding on host material affect attractivity of this host material to other H. abietis Pitfall traps baited with a combination of male or female weevils and cut stems of Scots pine caught more weevils of both sexes than pine alone. Weevils of either sex were not attractive in absence of host material. Attractivity of ground phloem containing weevil frass was not significantly different from that of ground phloem alone. In a laboratory test, feeding by weevils of either sex on pine about doubled the release of monoterpene hydrocarbons and ethanol compared with pine alone. Existence of an aggregation pheromone could not be confirmed. We suggest that weevil aggregations are formed in response to host volatiles and that weevil feeding increases amounts of these volatiles released.
TL;DR: Cabbage was grown interplanted with several living mulches and in bare-ground monocultures in 1982 and 1983 at Freeville, N.Y. and populations of Phyllotreta cruciferae Goeze and Brevicoryne brassicae (L.) were lower on cabbage grown with any living mulch than on cabbage in bare ground monoccultures.
Abstract: Cabbage was grown interplanted with several living mulches and in bare-ground monocultures in 1982 and 1983 at Freeville, N.Y. Living mulches were creeping bentgrass, red fescue, Kentucky bluegrass, and two white clovers. Populations of Phyllotreta cruciferae Goeze and Brevicoryne brassicae (L.) were lower on cabbage grown with any living mulch than on cabbage in bare-ground monocultures. First-generation larvae of Pieris rapae (L.) were more common on cabbage with clover living mulches, but second-generation eggs and larvae were less common on cabbage with clover living mulches. These differences in population density were probably determined by variation in herbivore colonization rates, not by variation in herbivore mortality. The data suggest that early season chemical treatments for flea beetles might be eliminated when living mulches are used. However, this potential gain may be offset by yield reduction from competition between cabbage and living mulches.
TL;DR: A biologically based phenology model is described for use in integrated pest management that predicts the proportion of insects in a population in various stages of development as a stochastic function of accumulated degree-days.
Abstract: A biologically based phenology model is described for use in integrated pest management. The model predicts the proportion of insects in a population in various stages of development as a stochastic function of accumulated degree-days. The model is based on a logistic probability distribution with mean and variance changing through time. Maximum likelihood parameters of the estimates are easily computed with nonlinear regression packages. Appropriate statistical tests are presented for comparing models. Results should be useful to researchers and biological modelers who describe insect or plant phenology.
TL;DR: Large-bodied mosquitoes are more successful at blood-feeding than are smaller individuals and the percent parous in the larger size classes was higher than in the smaller size classes.
Abstract: Resting and host-seeking adult female Psorophora columbiae (Dyar & Knab), Aedes atlanticus Dyar & Knab, Aedes vexans (Meigen), and Culex salinarius Coquillett were collected. Wing length and parity of each individual were determined. Results showed that average wing lengths within the four species did not differ between the resting and host-seeking populations. Parous C. salinarius and A. vexans had significantly longer wing lengths than did nulliparous females of the same species. Within each species, individuals were grouped in size classes of 1, 2, and 3 SD above and below the mean. In all four species, the percent parous in the larger size classes was higher than in the smaller size classes. Results indicate that large-bodied mosquitoes are more successful at blood-feeding than are smaller individuals.
TL;DR: Stink bug egg parasitism rates were surveyed at several locations in southern Louisiana during 1983 and 1984 and found eggs of Euschistus spp.
Abstract: Stink bug egg parasitism rates were surveyed at several locations in southern Louisiana during 1983 and 1984. Eggs of Euschistus spp. were parasitized most heavily. Parasitism of eggs of Nezara viridula (L.), Euschistus spp., Acrosternum hilare (Say), Podisus maculiventris (Say), and Edessa bifida (Say) varied between sample years. All parasitoid species collected were in the family Scelionidae. Telenomus podisi Ashmead was the most prevalent parasitoid during both 1983 and 1984. Parasitism by Trissolcus basalis Wollaston was high in 1983 but declined sharply the following year when populations of its primary host, N. viridula, were low. Apparent host switching was noted for both T. podisi and T. basalis from their primary hosts Euschistus spp. and N. viridula, respectively, when densities of all host masses increased. Trissolcus edessae Fouts and Trissolcus euschisti Fouts were collected both years at levels substantially below those of T. podisi and T. basalis. Telenomus calvus Johnson, a phoretic egg parasitoid of P. maculiventris, and Telenomus cristatus Johnson were collected incidentally during 1983. Parasitism of single egg masses by two different scelionid species was observed in all pentatomid hosts except E. bifida. In every case except one, both a Trissolcus species and T. podisi were involved. In the lone exception, both species were in the genus Trissolcus. Multiparasitism of individual eggs was not observed in this study.
TL;DR: A survey of 13 Willamette Valley, Oreg.
Abstract: A survey of 13 Willamette Valley, Oreg., commercial crops including apple, peach, prune-plum, cherry, filbert, grape, strawberry, raspberry, blackberry, corn, mint, and Christmas trees found Typhlodromus pyri Scheuten to be the principal phytoseiid present. Typhlodromus occidentalis Nesbitt, Amblyseius andersoni (Chant), A. aberrans (Oudemans), T. arboreus Chant, and A. fallacis (Garman) also were frequently collected. T. pyri was most prevalent on apple, prune, grape, and blackberry and usually on crops receiving few insecticide treatments. Seasonal differences in abundance were observed on some crops because T. pyri declined during mid- and late season as opposed to early season. T. occidentalis was significantly more abundant on apple and cherry than on other crops, and most prevalent in late season at heavily sprayed sites. A. andersoni was widespread among crops throughout the season but mostly limited to sites receiving few insecticide applications. A. aberrans was most abundant on filbert while A. fallacis was dominant on strawberry. T. arboreus was locally common on apple and prune. A slide-dip technique showed moderate resistance in T. pyri to azinphosmethyl (5- to 7-fold at the LC50) and high resistance to carbaryl (25- to 28-fold) and parathion (ca. 100-fold) at heavily treated field sites.
TL;DR: Late third instars of Mediterranean fruit fly, melon fly, and oriental fruitFly, that had exited the media to pupate were exposed to five concentrations of Steinernema feltiae, and pupae in puparia were not susceptible to S. feltiae.
Abstract: Late third instars of Mediterranean fruit fly, Ceratitis capitata (Wiedemann); melon fly, Dacus cucurbitae Coquillett; and oriental fruit fly, D. dorsalis Hendel, that had exited the media to pupate were exposed to five concentrations of Steinernema feltiae (=Neoaplectana carpocapsae) ranging from 500,000 to 5,000 per cup. Mean corrected percent mortalities 6 days after exposure ranged from 92 to 9% for Mediterranean fruit fly, 85 to 9% for the oriental fruit fly, and 86 to 0% for melon fly. Emerging Mediterranean fruit fly adults were marginally susceptible at 0.2% verified infection, and pupae in puparia were not susceptible to S. feltiae .
TL;DR: The study suggests that, in some circumstances, a subset of predator species could be more effective in reducing prey populations than the entire natural guild.
Abstract: Interspecific competition between two orb-weaving spiders, Metepeira grinnelli (Coolidge) and Cyclosa turbinata (Walckenaer), was investigated by selective removal of the predators. The estimated predation rate of small prey was higher where Cyclosa was alone than where both species were present, because when Metepeira was removed the density of Cyclosa became higher than the combined density of Metepeira and Cyclosa where both species were present and because the consumption rate of small prey by Metepeira was very low compared with that of Cyclosa. The study suggests that, in some circumstances, a subset of predator species could be more effective in reducing prey populations than the entire natural guild.
TL;DR: Three maize cultivars that had shown differences in response to Chilo partellus adults and larvae were evaluated for their relative ability to withstand larval infestation and damage, and foliar damage correlated better with yield loss than stalk tunneling.
Abstract: Three maize cultivars that had shown differences in response to Chilo partellus (Swinhoe) adults and larvae were evaluated for their relative ability to withstand larval infestation and damage. Three treatment regimes, protection by insecticides, artificial infestation, and natural infestation, were adopted. C. partellus was the predominant species during the whorl stage of crop development. Eldana saccharina Walker appeared during the tassel emergence stage and persisted through harvest. Treatment, cultivar, and interaction effects were significant for maize foliar damage, stalk breakage, and ear drop. Stalk tunneling was affected by treatment and cultivar effects but number of entrance holes per plant was affected by treatment only. A larval survival index, the ratio of exit to entrance holes per stem, was higher for ‘Inbred A’ than for the other cultivars, suggesting some antibiosis in the other cultivars. Yield reduction between the protected and infested treatments was 71.4% for ‘Inbred A’ compared with 3.1% for ‘ICZ2-CM’. Of the primary damage symptoms, foliar damage correlated better with yield loss than stalk tunneling. When the yield reduction and leaf damage responses of each cultivar were partitioned into quadrants, resistance in ‘ICZ1-CM’ and ‘ICZ2-CM’ appeared to be antibiosis perhaps together with tolerance or nonpreference, whereas ‘Inbred A’ had none of these qualities.
TL;DR: No correlation was found between size of egg batches and plant species, plant age, or position within a crop, but in chrysanthemum, moths deposited more eggs on younger than on older plants.
Abstract: Distribution of beet armyworm, Spodoptera exigua (Hubner), egg batches was similar in chrysanthemum, tomato, gerbera, and geranium crops grown in a greenhouse. Most eggs were laid on the underside of foliage on leaves within 10 cm of the soil surface. In chrysanthemum, moths deposited more eggs on younger than on older plants. No correlation was found between size of egg batches and plant species, plant age, or position within a crop.